Hormones

Edcexcel IGCSE Biology

Role of hormones

Chemical messengers produced by glands, transported by the bloodstream to target organs, regulating processes like growth, metabolism, and reproduction.

Endocrine system

A system of glands that secrete hormones into the bloodstream to control and coordinate various body functions.

Pituitary gland

A small gland at the base of the brain that controls other endocrine glands and secretes hormones like growth hormone, ADH (antidiuretic hormone), and FSH (follicle-stimulating hormone).

Thyroid gland

A gland in the neck that produces thyroxine, which regulates metabolism, growth, and development.

Adrenal glands

Glands located above the kidneys that produce adrenaline (fight or flight response) and cortisol (regulates metabolism and stress response).

Pancreas and its function

A gland that produces insulin (lowers blood glucose) and glucagon (raises blood glucose), regulating blood sugar levels.

Ovaries and their hormones

Female reproductive glands that produce estrogen and progesterone, controlling the menstrual cycle and pregnancy.

Testes and their hormone

Male reproductive glands that produce testosterone, responsible for sperm production and male secondary sexual characteristics.

Insulin function

Insulin lowers blood glucose levels by promoting glucose uptake into cells and storing excess as glycogen in the liver.

Glucagon function

Glucagon raises blood glucose levels by stimulating the liver to convert glycogen into glucose and release it into the bloodstream.

Thyroxine function

Thyroxine regulates metabolic rate, affecting growth, energy production, and temperature control.

Adrenaline function 7

1. It increases heart rate,

2. dilates pupils

3. releases glucagon to up raise blood sugar levels

4. diverts blood away from the digestive system towards you muscles

5. makes your hairs stand on end

6. breathing rate increase

7. mental awareness incresaes: faster reactions

Menstrual cycle hormones

• FSH (stimulates egg development)

• LH (triggers ovulation)

• oestrogen (builds uterine lining)

• progesterone (maintains pregnancy)

Negative feedback in hormone regulation

A process where a change in a hormone level triggers actions to counteract that change, maintaining balance (e.g., insulin and blood glucose regulation).

Type 1 diabetes

A condition where the pancreas produces little to no insulin, leading to high blood glucose levels. Treatment involves insulin injections.

Type 2 diabetes

A condition where the body becomes resistant to insulin, often linked to obesity. Management involves diet, exercise, and sometimes medication.

Estrogen function

A hormone produced by the ovaries that regulates the development of female secondary sexual characteristics and the menstrual cycle. It stimulates the thickening of the uterine lining in preparation for pregnancy.

Progesterone function

A hormone produced by the ovaries that prepares the uterus for pregnancy by maintaining the thickened uterine lining. A drop in progesterone causes menstruation. It also inhibits the release of further eggs during pregnancy.

FSH (Follicle-stimulating hormone) function

A hormone produced by the pituitary gland- when progesterone and oestrogen levels are low that stimulates the growth and development of egg follicles in the ovaries and promotes the production of eggs in females.

It releases oestrogen

LH (Luteinizing hormone) function

A hormone produced by the pituitary gland that triggers ovulation (release of an egg) and stimulates the production of progesterone in females.

ADH (Antidiuretic hormone) function

A hormone produced by the pituitary gland that regulates water balance by increasing water reabsorption in the kidneys, reducing urine output, and helping to maintain blood pressure and hydration levels.